Eh?
Well, it's good enough.
Just when I was looking through graphics cards a few days ago I saw the 460 GTX AND 260 GTX (I bought 260 GTX, 460 is gone).
Since they gave very little information on the boxes themselves, I'm only comparing what I saw.
If memory serves, 460 GTX had 790-something MB.
260 has 896MB.
Well, I'm not the best when it comes to comparing graphics cards but anything that will run VALVe games on high/highest settings will work for me (which 260 GTX seems to be capable of).
However, I have yet to see this for myself as I haven't installed it yet.